After Beren was brought before Thingol in Menegroth, and Beren declared his love for Lúthien, Thingol demanded a Silmaril from the Iron Crown of Morgoth. In return he would allow Beren to receive Lúthien as his bride, although Thingol deemed the task impossible, and thought rather that Beren would fail. Beren sought the help of Finrod Felagund, who owed Beren due to the service of Barahir, Beren's father. Therefore with ten companions they set out, disguised as Orcs, and were promptly captured by Sauron. Sauron held them prisoner in Tol-in-Gaurhoth, but he could not discern their identities or purpose. Therefore he sent a wolf to devour his prisoners one by one, until only Finrod and Beren were left. When the wolf came for Beren, an enraged Finrod fought tooth and nail with the wolf and killed it with his bare hands, which cost him his own life. After some time, Lúthien grew restless and approached her mother Melian for counsel. Melian told her that Beren was held captive in Sauron's fortress. Lúthien resolved to go and free him, but Thingol forbade this, and ordered for Lúthien to be guarded in a house built for her. But Lúthien used her magic to weave a cloak of enchantment, and she escaped from Doriath.

Lúthien encountered many perils along the way, running into Huan, the wolf hound of Valinor. The wolf brought her before his masters, Celegorm and Curufin. When she declared herself to them, the two sons of Fëanor were filled with wonder and feigned friendship to her. But they betrayed and restrained Lúthien, and she was held captive. Celegorm then intended to take Lúthien as his wife, and he sent emissaries to Thingol, demanding his allegiance. As Celegorm planned, the allegiance of Doriath would enhance the power of the Noldor, and further the war effort against Morgoth. Celegorm desired to unite all of the Elves of Middle-earth before he could attack Angband. But Huan took pity on Lúthien, having liked her from their first meeting. Eventually this prompted Huan to speak for the first of three times. He gave Lúthien advice, and freed her from captivity. He bore Lúthien away, and humbled his pride by becoming her steed.

They came at last to Tol-in-Gaurhoth, and Sauron was aware of them. He sent wolf after wolf to the gate, but Huan slew them one by one. Then Sauron, who knew of Huan's fate, imagined that he himself could be the one to end Huan. Sauron came forth himself in the shape of a terrible wolf, and both Lúthien and Huan quailed before him. But as Sauron advanced, Lúthien flung her cloak over Sauron's face, and he was struck by the blinding enchantment of weariness. Huan used the opportunity to take Sauron by the throat. Sauron tried to escape by shape shifting, but Huan held him down. Lúthien then demanded Sauron to yield the mastery of the tower to her, less Huan should destroy his mortal form. Sauron yielded, and fled the scene. Lúthien, having received mastery of the tower, laid waste to the fortress with her magic. The walls were destroyed and the prisons were broken. Lúthien found Beren and healed him.

United once more, they were later ambushed by Celegorm and Curufin, who knew of Beren's intentions to wrest a Silmaril from Morgoth. But Huan turned against them, and with his aid Beren defeated the sons of Fëanor. While they fled, Curufin shot an arrow at Lúthien, but Beren stood in its path and was stuck in the chest. Huan chased the princes away, and returned with herbs to cure Beren. With some effort, Lúthien healed Beren. But Beren resolved to carry on his quest without Lúthien, but she denied him this. Huan spoke for a second time, advising that they were now bound together, whether Beren will it or not. Therefore the two of them headed for Angband, and were brought before the throne of Morgoth himself. Lúthien was undaunted by Morgoth, and she offered to dance and sing for him in the manner of a minstrel. Morgoth beheld her with lust, of which came a secret desire to do some unspeakable evil to Lúthien. Morgoth accepted for this reason, but Lúthien sang a song of such enchantment that Morgoth and his court fell into a deep sleep.

Beren then used the opportunity to cut a Silmaril from Morgoth's crown. The Silmaril did not burn him, and Beren thought of going beyond his vow and retrieving all three of the Silmarils. But as he began to cut a second one loose, the knife broke, and a shard struck Morgoth in the face. Morgoth and his court stirred, and Lúthien and Beren fled for their lives. At the gate however they were ambushed by Carcharoth, Morgoth's wolf. Beren tried to ward him off with the light of the Silmaril, but Carcharoth desired it and bit off Beren's hand. But the Silmaril burned the wolf's innards, and caught in excruciating pain, Carcharoth fled. In his madness he passed through the Girdle of Melian into Doriath, thanks to the power of the Silmaril.

Beren was nursed to health once more by Lúthien, and they returned to Doriath. Thingol was amazed to see Beren alive, but he still disliked him for the doom he had brought on Doriath. But Beren told him of his tale, and that a Silmaril was in his other hand. Thingol's mood towards Beren then changed, and at last he yielded Lúthien to him. Eventually Carcharoth was discovered by Thingol's warriors, and the wolf was attacked. Thingol was nearly slain, but Beren saved him and was mortally wounded. Huan then fought with Carcharoth and slew him, with both wolves dying. The Silmaril was cut from Carcharoth's burned flesh, and Beren presented it at last to Thingol before he died. Thingol then held Beren with respect, but Lúthien commanded Beren to wait for her in the Undying Lands. Lúthien passed away in grief, and her spirit came to the halls of Mandos. There she sang a song of woe and lamentation, and Mandos himself was moved to pity. He then summoned Beren's spirit, and the two were reunited. But though Mandos pitied them, Lúthien was faced with a choice; to remain in Valinor and its eternal bliss, or for her and Beren to return to Middle-earth as mortals, after which they would die a second death. Lúthien chose the latter, and she and Beren returned to Doriath.

Many rejoiced at their return. But when Melian saw her daughter again, by virtue of being an Ainur, she foresaw that a parting beyond the world was now due. Melian was grieved, knowing that Lúthien would soon vanish forever. But the Quest was completed; Thingol had received the Silmaril, and Beren had won Lúthien.

The Silmaril retrieved from Morgoth's crown would bring about dramatic changes. The first change was the doom of Doriath. Unfortunately, in naming the desire of the Silmaril, Thingol had awoken the curse of Mandos. Just as Finrod warned Beren, those who so much as name a Silmaril in desire moves a great power from slumber, namely the Oath of Feanor. Before long, the Sons of Fëanor sent messages demanding the return of the jewel. Melian counselled Thingol to give it up, and save Doriath from its doom. But Thingol was angered by the prideful words of the messages, and since the jewel had been won by the efforts of Beren and Lúthien, he refused. He instructed the the Dwarves of Nogrod to reconstruct the Nauglamir so that it would hold the Silmaril. But the Dwarves, desiring the Silmaril and the Nauglamir for themselves, slew King Thingol and tried to escape with the treasure. Most of them were slain and the Silmaril was returned to Melian. But it did little to soothe Melian, and she was overcome with grief. Melian departed from Middle-earth and returned to Valinor, and the enchantment which had fenced Doriath from evil vanished in her absence.

This allowed for Doriath's eventual destruction by the sons of Feanor, when they tried to reclaim the Silmaril from Dior. They failed however, and the Silmaril was passed onto Elwing, Dior's daughter. Eventually the sons of Feanor tracked her down too, which led to the assault on the Mouths of Sirion. Elwing still managed to escape with the Silmaril.

Though Morgoth did not count the missing Silmaril as a great loss, it would soon result in his downfall. Elwing and her husband Earendil were guided to Valinor by the Silmaril, and there Earendil pleaded with the Valar to forgive the sins of the Noldor and put an end to the darkness. The Valar granted his plea, and the lone Silmaril was set in the sky as a star. The Valar assembled a mighty host in the War of Wrath, which resulted in Morgoth's final defeat.